The mowing shorter recommendation goes against everything I've done up until this year. I was a great fan of leaving the height grow to 4", then mowing it down to three. Then, last fall, the Magnificent Twenty of us put in these premium cultivars for new lawns (Mag 3 mix, more or less, for most of us, but modified a cultivar here, a cultivar there), and we (and the original poster) now have 'dwarf' species, or 'compact' species of bluegrass, starting with Midnight or Midnight II. I fear that 'compact' or 'dwarf' means 'short', at least in the short term (first full year of establishment). What the OP needs at present is a way to get the new grass spreading out, even if it's at the cost of somehow 'less than optimal' if optimal means more height, more roots, but less spreading this year. I believe a thread here in the forum supports this strategy. Everybody seems to be encountering (in April) a low-growth habit, and a need of fertilizer. We know that KBG is a 'heavy feeder', requires more fert than other lawns. We know that new KBG lawns require even more fert than that, although some of us aren't going to put it down that heavily. We should. That new KBG is coming in pretty low to the ground. Lower than we are used to. I think the literature will support the proposition that the new lawn should be mowed shorter than we would have mowed our old KBG lawns, last year, if what we want this year is maximum 'spreading' as opposed to maximum 'taller'. No question the poa can survive. It will be there til the heat of summer. But the dose of pre-M in summer, followed by another dose of pre-M in the fall, should go far toward seeing that those poa seeds don't germinate this fall (and I think that most of us know that poa germinates in the fall, not in the spring). At that point, what's left on that lawn? With luck, brand new KBG, at the end of its first full season. With maximum spreading. Since there isn't going to be much spreading in the heat of July and August, that's got to be done this spring, when that grass stand is immature. Which prompted the somewhat counter-intuitive advice to mow it shorter than usual, this first full season. I do believe that all of us, in the Magnificent Twenty are going to end up mowing shorter than we're used to, say, up to the 4th of July. We'll have to wait until the reports come in, to see if that's the case. But the Original Poster can't kill poa now, he's got to wait til fall, and kill the seeds, with the pre-emergent. And he's got to have a pretty well spread out stand of new KBG there, when the poa goes away.

Nothing right now! The window for seeding is closed, even down there in KY. Once the season heads into winter--probably January--consider scattering a normal seeding rate of seed in the holes, with proportionate amounts in thin areas. That'll settle in, happily undergo pre-germination, and if everything goes well in spring (it does about half the time), sprout when it can. Fortunately, grass is not impacted by frost, so the normal temperature changes towards the end of the late-winter season won't matter in the slightest. Even minor ground re-freezes aren't overly harmful. You can also dormant seed (which is the above procedure) as late as just before soil temperatures rise above fifty--anywhere in the below-fifty window is just fine. So until the forsythia are in full bloom, you're golden. Other than that, control weeds as necessary by spot spraying, realizing that you're going to kill a little of the newly-sprouted grass when you do that (the stuff that went through winter will be just fine). But I don't recommend letting weeds get a foothold in spring--nor do I recommend Weed and Feed, which will destroy the new grass wholesale, nor blanket spraying, which will do the same.

Where do you live? When do you expect frost? KBG takes 2-3 weeks or more to germinate and it is difficult to do in an overseeding as the existing grass will outcompete and shade it. When you mow you would be disturbing ungerminated seed. If you have rye, best to stay with rye. Rye germinates quickly. If you want KBG, plan to renovate (kill everything first and fallow) next July/August (July for killing and fallowing, mid to late August for seeding). It's probably unnessary to aerate and dethatch. Cut low as planned, bagging clippings. A light raking will be helpful. A pre-emergent next spring when the forsythia blooms will help prevent summer weeds.

Taking care of your own lawn will result in a nicer lawn that you have confidence in. You'll know what's going on and why. Also you won't waste resources or damage your environment. Sod is a good idea in the spring. When you seed in the spring you get a lot of weeds coming in with the new grass. Further, new spring grass does not develop good roots before the hot weather hits. The end result is you have crabgrass in those spots by July. If you want to begin mixing Kentucky bluegrass into your lawn, that will help keep the bare spots to a minimum. KBG spreads to fill thin areas whereas fescue and rye grasses do not. Apply preemergent when the forsythia begins to bloom in your neighborhood. Spot spray weeds in April. Fertilize in late May (Memorial Day) Fertilize in early fall (Labor Day) Fertilize again with a high N (low to 0 P and K) fast release fertilizer after your grass stops growing in late fall but before the frost takes it to complete dormancy. The idea is to get nutrients into the roots without stimulating new growth that late in the season. This is "winterizer." It will help the grass come out of dormancy in the spring. In addition to, or in place of, one of the fertilizer drops, I would use an organic fertilizer. Organic fertilizer works differently from chemical fertilizers. The organic will improve the health of your soil as much as helping your grass green up and grow. Mulch mow at your mower's highest setting for your lawn. Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall. You should not get a disease following this plan. Most bugs you see in the lawn are beneficial. There is always a chance of getting bugs that are not good. Usually you would see the damage in August, so the time to inspect the lawn for them is in late June. If you don't see a lot of Japanese beetles swarming your porch lights in May or June then you probably won't have a grub problem. Good luck taking this on. As you can see it is fairly straight forward and not hard.